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individual computers in the network and allocates their resources to Distributed OS •Presents users (and applications) with an integrated computing platform that hides the individual computers. •Has control over all of the nodes (computers) in the network and allocates their resources to tasks without user involvement. – In a distributed OS, the user doesn't know (or care) where his programs are running. • Examples: – Amoeba (http://amoebaos.org)(http://amoebaos.or – EyeOS (www.eyeos.org)(www.eyeos.org

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More examples ICloud

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j li l d MoreExamples jolicloud G.HO.ST Glide os

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Daftar webOS

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T / URL Failure DOS:Transparency – Users are not the resources aware of the positioning in the system. of names / URL – Users should not be aware of the presence of multiple copies of a resource • Failure Transparency – Masking the partial failures in the system • Migration Transparency – Resources can move without changing • Replication Transparency • Location Transparency

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’d Performance Transparency Cont d... performance of the system knowledge of the user. Userssees only speedup. – Allowing the system to expand in scale without disrupting the activities of the users • Performance Transparency – Reconfiguring the resources to improve the • Concurrency Transparency – Resource sharing is automatic • Parallelism transparency – Activities can happen in parallel without the • Scaling Transparency

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1.14 Distributed OperatingSystems

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The differences NOS DOS

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A b i Th l i h Wh i i i i d h WhatisAmoeba? •••• Runs on a simple micro-kernel Developed by Andrew Tanenbaum • Has user transparency – The user logs into the system not a specific machine – When a program is initiated, the system decides what machine will run it. • Amoeba is a distributed operating system

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• Fireball Amoeba TheHistoryof Amoeba •Developed by Andrew Tanenbaum at Vrije Universiteit in conjunction with the •Others have developed their own versions – Fireball Amoeba by Fireball Software Distribution Centrum voor Wiskunde en Informatica • First prototype was released in 1983 • The last official update was in 1996

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Th f i l GoalsofAmoeba • Connecting together many machines Parallelism • Allowing individual jobs to use multiple easily Transparency – CPUs – • Having the collection of computer act like a single system Performance – • There are four main goals – Distribution

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Micro-kernel Key Concepts • –––––– A simple micro-kernel is the basis for Amoeba All computers in the network run this kernel It handles the memory management, I/O, communication, object primitive, and basic processes •Remote Procedure Calls (RPC) – Used for communication between client and server – Accessed by stubs which are created by Amoeba Interface Language

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KeyConcepts •Objects – The abstract data type used by Amoeba – Each object has a list of operations that can be preformed Capability (Protection) • –––– Store data in 128 bit value Used to verify that the user has permission to access the object Capabilities are encrypted –

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KeyConcepts •Bullet / File Server – Store files in a contiguously fashion – Designed to be a deicatedserver •Directory Server – Handles naming of files – Knows the physical loc tioof eachfile – Most files can be sent in a single RPC

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The system is free •••••• It has not had an official update in over 10years Can use powerful older/slower CPUs to system createa •Can only hold programsas large as itsphysical memory •Micro-Kernel allows for other file systems to be created • Has many UNIX like commands and programs